阅读说明：本技术 一种陶瓷隔膜及其制备方法以及二次电池 (Ceramic diaphragm, preparation method thereof and secondary battery ) 是由 项海标 于 2021-08-02 设计创作，主要内容包括：本发明属于隔膜技术领域,尤其涉及一种陶瓷隔膜及其制备方法以及二次电池,包括：基膜；陶瓷涂层,设置于所述基膜至少一侧面,陶瓷涂层包括无机填料、纳米线材料。本发明的一种陶瓷隔膜,具有良好的机械强度、耐高温性和对电解液具有良好的吸液率,而且厚度薄。(The invention belongs to the technical field of diaphragms, and particularly relates to a ceramic diaphragm, a preparation method thereof and a secondary battery, wherein the ceramic diaphragm comprises the following components: a base film; the ceramic coating is arranged on at least one side surface of the base film and comprises inorganic filler and nanowire materials. The ceramic diaphragm provided by the invention has the advantages of good mechanical strength, high temperature resistance, good liquid absorption rate to electrolyte and thin thickness.)

1. A ceramic diaphragm, comprising:

a base film;

the ceramic coating is arranged on at least one side surface of the base film and comprises inorganic filler and nanowire materials.

2. The ceramic separator of claim 1, further comprising a polymer coating disposed on a side of the base film remote from the ceramic coating and/or on a side of the ceramic coating remote from the base film.

3. The ceramic separator according to claim 1, wherein the ceramic coating has a thickness of 1-2 μm.

4. The ceramic separator according to claim 1, wherein the inorganic filler is a rod-shaped inorganic filler, the nanowire material has a diameter of 1 to 100nm, the nanowire material includes long nanowires having an aspect ratio of 500 or more and 5000 or less, and short nanowires having an aspect ratio of 10 or more and 400 or less.

5. The preparation method of the ceramic diaphragm is characterized by comprising the following steps:

step (A): adding an inorganic filler and a nanowire material into a first solvent, stirring and mixing, grinding, adding a first binder, stirring and mixing to obtain an inorganic slurry;

step (B): coating the inorganic slurry prepared in the step (A) on at least one side of a base film to obtain the ceramic diaphragm.

6. The preparation method of the ceramic separator according to claim 5, wherein the weight part ratio of the inorganic filler to the nanowire material is 30-70: 20 to 80 parts.

7. The method of manufacturing a ceramic separator according to claim 6, wherein the inorganic slurry further comprises 0.1 to 10 parts by weight of a first dispersant, 0.1 to 10 parts by weight of a first thickener, and 0.1 to 5 parts by weight of a first wetting agent, and the inorganic slurry, the nanowire material, the first dispersant, and the first thickener are added to the first solvent and mixed by stirring, ground, and added with the first wetting agent and 0.1 to 10 parts by weight of a first binder and mixed by stirring to obtain the inorganic slurry.

8. The method for preparing the ceramic separator according to claim 7, further comprising adding a second dispersing agent, a second thickening agent and a polymer main material into a second solvent, stirring and dispersing, grinding, adding a second adhesive and a second wetting agent, stirring and dispersing to obtain a polymer slurry, and coating the polymer slurry on the side of the base film away from the ceramic coating and/or the side of the ceramic coating away from the base film to form the polymer coating, thereby preparing the ceramic separator.

9. The preparation method of the ceramic separator according to claim 8, wherein the weight ratio of the polymer main material, the second dispersing agent, the second thickener, the second binder and the second wetting agent is 3-50: 0.1-5.

10. A secondary battery comprising a positive electrode, a negative electrode, a separator for separating the positive electrode and the negative electrode, an electrolyte, and a case, wherein the separator is the ceramic separator according to any one of claims 1 to 4.

Technical Field

The invention belongs to the technical field of diaphragms, and particularly relates to a ceramic diaphragm, a preparation method thereof and a secondary battery.

Background

The lithium ion battery has the characteristics of high working voltage, high energy density, long cycle life, no memory effect, no pollution and the like, has the advantages of quick charge and discharge and the like, is a main energy source of various electronic products, and is a green environment-friendly pollution-free secondary battery. Meanwhile, the lithium battery meets the development requirements of energy and environmental protection in various countries at present, so that the use amount of various industries is increased rapidly, and the safety, the capacity, the service life and the like of the lithium battery are more and more valued by people.

The four key materials of the lithium ion battery are a positive electrode material, a negative electrode material, electrolyte and a diaphragm. The diaphragm has the main functions of isolating the positive electrode and the negative electrode and preventing electrons from passing through, and can allow ions to pass through, so that the lithium ions are rapidly transmitted between the positive electrode and the negative electrode in the charging and discharging process. In order to improve the safety, capacity and cycle life of lithium batteries, the thickness, thermal shrinkage and liquid absorption and retention of the separator are important for research. At present, people can already prepare a ceramic diaphragm with the thickness of 1-2 mu m by controlling the granularity of ceramic powder, but because the coating is too thin, the composite membrane has a great defect in the aspect of high-temperature heat resistance, the liquid absorption and retention capacity of electrolyte is greatly reduced, and the safety of a lithium battery is extremely unfavorable.

Disclosure of Invention

One of the objects of the present invention is: aiming at the defects of the prior art, the ceramic diaphragm is provided, has good mechanical strength, high temperature resistance and good liquid absorption rate to electrolyte, and is thin.

In order to achieve the purpose, the invention adopts the following technical scheme:

a ceramic diaphragm comprising:

a base film;

the ceramic coating is arranged on at least one side surface of the base film and comprises inorganic filler and nanowire materials.

As an improvement of a ceramic separator of the present invention, the ceramic separator further includes a polymer coating layer disposed on a side of the base film remote from the ceramic coating layer and/or disposed on a side of the ceramic coating layer remote from the base film.

As an improvement of the ceramic diaphragm, the thickness of the ceramic coating is 1-2 μm.

As an improvement of the ceramic diaphragm, the inorganic filler is a rod-shaped inorganic filler, the diameter of the nanowire material is 1-100nm, the nanowire material comprises a long nanowire and a short nanowire, the length-diameter ratio of the long nanowire is greater than or equal to 500 and less than or equal to 5000, and the length-diameter ratio of the short nanowire is greater than or equal to 10 and less than or equal to 400.

The second purpose of the invention is: aiming at the defects of the prior art, the preparation method of the ceramic diaphragm is simple, easy to operate and control and capable of realizing mass production.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a ceramic diaphragm comprises the following steps:

step (A): adding an inorganic filler and a nanowire material into a first solvent, stirring and mixing, grinding, adding a first binder, stirring and mixing to obtain an inorganic slurry;

step (B): coating the inorganic slurry prepared in the step (A) on at least one side of a base film to obtain the ceramic diaphragm.

As an improvement of the preparation method of the ceramic diaphragm, the weight part ratio of the inorganic filler to the nanowire material is 30-70: 20 to 80 parts.

The inorganic slurry further comprises 0.1-10 parts by weight of a first dispersing agent, 0.1-10 parts by weight of a first thickening agent and 0.1-5 parts by weight of a first wetting agent, the inorganic slurry, the nanowire material, the first dispersing agent and the first thickening agent are added into the first solvent and stirred and mixed, grinding is carried out, and the first wetting agent and 0.1-10 parts by weight of a first binding agent are added and stirred and mixed to obtain the inorganic slurry.

The preparation method of the ceramic diaphragm is improved by adding the second dispersing agent, the second thickening agent and the polymer main material into the second solvent, stirring and dispersing, grinding, adding the second adhesive and the second wetting agent, stirring and dispersing to obtain polymer slurry, and coating the polymer slurry on the side of the base film far away from the ceramic coating and/or the side of the ceramic coating far away from the base film to form the polymer coating, so that the ceramic diaphragm is prepared.

As an improvement of the preparation method of the ceramic diaphragm, the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 3-50: 0.1-5.

The third purpose of the invention is that: aiming at the defects of the prior art, the secondary battery has high energy density, good mechanical strength and high temperature resistance and good safety.

In order to achieve the purpose, the invention adopts the following technical scheme:

a secondary battery comprises a positive electrode, a negative electrode, a diaphragm, electrolyte and a shell, wherein the diaphragm is used for separating the positive electrode from the negative electrode, and the diaphragm is the ceramic diaphragm.

Compared with the prior art, the invention has the beneficial effects that: the ceramic diaphragm disclosed by the invention is matched with the nano-wire material by using the inorganic filler, so that the liquid absorption performance of the diaphragm is improved, the mechanical strength, the high temperature resistance, the heat shrinkage and the puncture resistance of the diaphragm are also improved, and the nano-wire material is smaller in size, so that the thickness of the whole ceramic diaphragm is thinner, the thickness and the volume can be reduced, and the energy density of a battery is increased.

Drawings

Fig. 1 is a schematic flow chart of a method for manufacturing a ceramic separator according to the present invention.

Fig. 2 is a schematic structural view of a ceramic diaphragm of the present invention.

Fig. 3 is a schematic structural view of a ceramic separator according to example 1 of the present invention.

Fig. 4 is a schematic structural view of a ceramic diaphragm according to example 2 of the present invention.

Fig. 5 is a schematic structural view of a ceramic diaphragm according to example 3 of the present invention.

Fig. 6 is a schematic structural view of a ceramic diaphragm of example 4 of the present invention.

Fig. 7 is a graph showing the effect of the present invention after coating using a circular pattern roll.

FIG. 8 is a graph showing the effect of the invention after coating with a square pattern roll.

FIG. 9 is a graph showing the results of wettability testing in example 1 of the present invention.

FIG. 10 is a graph showing the results of the wettability test of comparative example 1 of the present invention.

Wherein: 1. a base film; 2. a ceramic coating; 3. and (3) coating a polymer.

Detailed Description

1. A ceramic diaphragm comprising:

a base film 1;

and the ceramic coating 2 is arranged on at least one side surface of the base film 1, and the ceramic coating 2 comprises inorganic filler and nanowire materials.

The ceramic diaphragm provided by the invention has the advantages of good mechanical strength, high temperature resistance, good liquid absorption rate to electrolyte and thin thickness. The invention uses the matching use of the inorganic coating and the organic coating, so that the prepared ceramic diaphragm not only has the basic function of the ceramic diaphragm, but also has better high-temperature thermal shrinkage performance, puncture resistance and mechanical strength, and particularly solves the problem that the thermal shrinkage of the 1 mu m coating is larger at 150 ℃, and the thermal shrinkage of the 1 mu m coating is less than 5 percent at 150 ℃ for 0.5 h.

Preferably, the ceramic diaphragm further comprises a polymer coating 3, wherein the polymer coating 3 is arranged on the side of the base film 1 far away from the ceramic coating 2 and/or on the side of the ceramic coating 2 far away from the base film 1. The polymer coating 3 can increase the adhesion between the ceramic diaphragm and the pole piece and improve the hardness of the battery core.

Preferably, the thickness of the ceramic coating 2 is 1-2 μm. The ceramic coating 2 of the invention uses nano materials, which can greatly reduce the thickness of the ceramic coating 2, thereby making the whole thickness of the prepared ceramic diaphragm thinner and having the performance of the diaphragm.

Preferably, the inorganic filler is a rod-shaped inorganic filler, the diameter of the nanowire material is 1-100nm, the nanowire material comprises a long nanowire and a short nanowire, the aspect ratio of the long nanowire is greater than or equal to 500 and less than or equal to 5000, and the aspect ratio of the short nanowire is greater than or equal to 10 and less than or equal to 400. The length-diameter ratio can influence the efficiency of constructing the coating network structure, and the stable coating network structure can be better formed by selecting the proper length-diameter ratio. The length-diameter ratio is too large, the flexibility of the nanowire is very good, and agglomeration and knotting can be caused by slight improper treatment. The aspect ratio is too small and the network formed is not tight enough and is too packed.

2. The preparation method of the ceramic diaphragm is characterized by comprising the following steps:

step (A): adding an inorganic filler and a nanowire material into a first solvent, stirring and mixing, grinding, adding a first binder, stirring and mixing to obtain an inorganic slurry;

step (B): coating the inorganic slurry prepared in the step (A) on at least one side of the base film 1 to obtain the ceramic separator.

The preparation method of the ceramic diaphragm is simple in preparation, easy to operate and control and capable of realizing mass production. The rotation speed of stirring and dispersing after the first solvent is added in the step (A) is 20-50rpm, the dispersion rotation speed is 500-3000rpm after the first adhesive is added, and the stirring and dispersing time is 20-60 min. The rotation speed of the grinding in the step (A) is 600-. The inorganic filler of the invention is Al₂O₃、Al(OH)₃And one or more inorganic fillers in a rod shape can be combined with the nanowire material to form a loose net structure, so that the mechanical strength of the diaphragm is improved, and the high porosity can improve the adsorption and wetting property of electrolyte, so that the liquid retention and mechanical strength of the diaphragm are improved. As shown in fig. 1, the method for manufacturing a ceramic separator according to the present invention first prepares an inorganic slurry and a polymer slurry (the order of preparing the slurries is not specified), coats the inorganic slurry on both sides of a base film 1 to form an inorganic coating, coats the polymer slurry on the surface of the inorganic coating to form a polymer coating 3, and may form the inorganic coating on one side of the base film 1 and the polymer coating 3 on the other side of the base film 1.

Preferably, the weight part ratio of the inorganic filler to the nanowire material is 30-70: 20 to 80 parts. The proportion of the inorganic filler and the nanowire material is reasonably controlled, so that the ceramic coating 2 prepared by mixing has the advantages of mechanical strength, high temperature resistance, liquid absorption rate and puncture resistance.

Preferably, the inorganic filler is a rod-shaped inorganic filler, the diameter of the nanowire material is 1-100nm, the nanowire material comprises a long nanowire and a short nanowire, the aspect ratio of the long nanowire is greater than or equal to 500 and less than or equal to 5000, and the aspect ratio of the short nanowire is greater than or equal to 10 and less than or equal to 400.

Preferably, the inorganic slurry further comprises 0.1-10 parts by weight of a first dispersing agent, 0.1-10 parts by weight of a first thickening agent and 0.1-5 parts by weight of a first wetting agent, and the inorganic slurry, the nanowire material, the first dispersing agent and the first thickening agent are added into the first solvent and stirred and mixed, ground, and added with the first wetting agent and 0.1-10 parts by weight of a first binder and stirred and mixed to obtain the inorganic slurry.

Preferably, the preparation method of the ceramic diaphragm further comprises the steps of adding the second dispersing agent, the second thickening agent and the polymer main material into the second solvent, stirring and dispersing, grinding, adding the second adhesive and the second wetting agent, stirring and dispersing to obtain polymer slurry, and coating the polymer slurry on the side of the base film 1 far away from the ceramic coating 2 and/or the side of the ceramic coating 2 far away from the base film 1 to form the polymer coating 3, so as to prepare the ceramic diaphragm. The polymer main material is one or more organic polymers of PVDF and PMMA, the melting point is 100-350 ℃, the addition amount in the polymer slurry is 3-50%, the coating thickness is 0.2-10 mu m, and the coating gram weight is 0.05-5.0g/m²And the bonding strength of the isolating film and the pole piece can be improved. The inorganic coating and the organic coating are matched for use, so that the diaphragm not only has good mechanical property, temperature resistance, high liquid absorption rate and puncture resistance, but also has better adhesion with a pole piece, and the hardness of the diaphragm is improved. The polymer paste coating can be performed using a pattern roll, the pattern of which is one of hexagonal, negative dot, S-shaped, circular, and square, wherein fig. 7 is a graph of the effect after coating using a roll with a circular pattern, and fig. 8 is a graph of the effect after coating using a roll with a square pattern.

Preferably, the first thickener and/or the second thickener is one or more of sodium carboxymethyl cellulose, methyl cellulose, carboxymethyl cellulose and sodium alginate. The first binder and/or the second binder are/is one or more of polyvinyl alcohol, styrene-butadiene rubber, styrene-acrylic latex, pure benzene latex and fluoride; the first dispersant and/or the second dispersant is one or more of sodium polyacrylate, sodium dodecyl sulfate, carboxylate fluorine dispersant and sulfonate fluorine dispersant; the first wetting agent and/or the second wetting agent is one or more of sodium polyacrylate, polyoxyethylene alkylphenol ether and alkylphenol polyoxyethylene ether.

Preferably, the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 3-50: 0.1-5.

Preferably, the base film 1 is a PE, PP or PE/PP/PE composite isolating film, the melting point of the base film 1 is 130-160 ℃, the thickness is 3-16um, the porosity is 20-50%, and the air permeability is 30-300sec/100 cc.

A secondary battery comprises a positive electrode, a negative electrode, a diaphragm, electrolyte and a shell, wherein the diaphragm is used for separating the positive electrode from the negative electrode, and the diaphragm is the ceramic diaphragm.

The secondary battery has high energy density, good mechanical strength and high temperature resistance, and good safety.

Wherein, the positive electrode comprises a positive electrode current collector and a positive electrode active material arranged on the positive electrode current collector, and the positive electrode active material can be a chemical formula including but not limited to Li_aNi_xCo_yM_zO_2-bN_b(wherein a is more than or equal to 0.95 and less than or equal to 1.2, x>0, y is more than or equal to 0, z is more than or equal to 0, and x + y + z is 1,0 is more than or equal to b and less than or equal to 1, M is selected from one or more of Mn and Al, N is selected from one or more of F, P and S), and the positive electrode active material can also be selected from one or more of LiCoO (lithium LiCoO), but not limited to₂、LiNiO₂、LiVO₂、LiCrO₂、LiMn₂O₄、LiCoMnO₄、Li₂NiMn₃O₈、LiNi_0.5Mn_1.5O₄、LiCoPO₄、LiMnPO₄、LiFePO₄、LiNiPO₄、LiCoFSO₄、CuS₂、FeS₂、MoS₂、NiS、TiS₂And the like. The positive electrode active material may be further modified, and the method of modifying the positive electrode active material is known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, and the like, and the material used in the modification may be one or a combination of more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, and the like. And the positive electrode current collector is generally a structure or a part for collecting current, and the positive electrode current collector may be any material suitable for being used as a positive electrode current collector of a lithium ion battery in the field, for example, the positive electrode current collector may include, but is not limited to, a metal foil and the like, and more specifically, may include, but is not limited to, an aluminum foil and the like.

The negative electrode comprises a negative electrode current collector and a negative electrode active substance arranged on the surface of the negative electrode current collector, wherein the negative electrode active substance can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming alloys with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. The negative electrode current collector is generally a structure or a part for collecting current, and the negative electrode current collector may be any material suitable for use as a negative electrode current collector of a lithium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.

The separator may be any material suitable for a lithium ion battery separator in the art, and for example, may be a combination including, but not limited to, one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like.

The lithium ion battery also comprises electricityAnd the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte₆And/or LiBOB; or LiBF used in low-temperature electrolyte₄、LiBOB、LiPF₆At least one of; or LiBF used in anti-overcharge electrolyte₄、LiBOB、LiPF₆At least one of, LiTFSI; may also be LiClO₄、LiAsF₆、LiCF₃SO₃、LiN(CF₃SO₂)₂At least one of (1). And the organic solvent may be a cyclic carbonate including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, control of H in the electrolyte₂At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.

The material of the shell includes but is not limited to one of aluminum plastic film, aluminum plate, tin plate and stainless steel.

The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.

Example 1

1. A ceramic diaphragm comprising:

a base film 1;

the ceramic coating 2 is arranged on two side surfaces of the base film 1, and the ceramic coating 2 comprises an inorganic filler and a nanowire material;

and a polymer coating 3 disposed on both sides of the ceramic coating 2 away from the base film 1.

2. A preparation method of a ceramic diaphragm comprises the steps of weighing 50 parts of alumina, 25 parts of long nanowires (carbon nanotubes) and 25 parts of short nanowires (carbon nanotubes), adding the materials into pure water in steps respectively, stirring and dispersing the materials, wherein the stirring rotation speed is 30R, the dispersion rotation speed is 2000R, and stirring the materials for 30min respectively to obtain a mixed solution 1; continuously adding 0.5 part of sodium dodecyl sulfate and 0.2 part of sodium carboxymethyl cellulose (low viscosity, 1% solution viscosity at 25 ℃ of 1500-; after grinding, respectively adding 4 parts of styrene-acrylic emulsion and 0.2 part of polyoxyethylene alkylphenol ether into the semi-finished slurry, slowly stirring at the stirring speed of 25R and the dispersion speed of 800R for 30min, and filtering to obtain inorganic slurry; 0.5 part of carboxylate fluorine dispersant, 0.5 part of sodium carboxymethylcellulose (with high viscosity, 1% solution viscosity of 25 ℃, 3500 & lt- & gt 5500mpa. s), 35 parts of PMMA polymer solution and 1 part of polyvinyl alcohol are sequentially added into pure water, the stirring speed is 30R, the dispersion speed is 1500R, the time is 30min respectively, and finally 0.5 part of alkylphenol ethoxylate is added into the mixed solution for slow stirring, the stirring speed is 20R, the dispersion speed is 800R, and the time is 20 min. And filtering to obtain polymer slurry after stirring, coating inorganic slurry by using a diagonal roll gravure coater to obtain a ceramic coating 2 with the thickness of 1.5um, and coating polymer coatings 3 with the thickness of 0.25um on two sides of the inorganic coating film by using a hexagonal gravure roll to obtain a ceramic diaphragm, wherein as shown in figure 3, the inorganic coatings are arranged on two side surfaces of the base film 1, and the polymer coatings 3 are arranged on the side surfaces of the inorganic coatings far away from the base film 1.

As shown in fig. 1, the method for manufacturing a ceramic separator according to the present invention first prepares an inorganic slurry and a polymer slurry (the order of preparing the slurries is not specified), coats the inorganic slurry on both sides of a base film 1 to form an inorganic coating, coats the polymer slurry on the surface of the inorganic coating to form a polymer coating 3, and may form the inorganic coating on one side of the base film 1 and the polymer coating 3 on the other side of the base film 1.

3. A secondary battery comprises a positive electrode, a negative electrode, a diaphragm, electrolyte and a shell, wherein the diaphragm is used for separating the positive electrode from the negative electrode, the diaphragm is the ceramic diaphragm, the positive electrode uses aluminum foil, and the negative electrode uses graphite. And cutting the prepared diaphragm into 19mm circular sheets by using a slicer, drying the sliced diaphragm at a 100 ℃ hot bench for 2h to remove residual moisture, and assembling the prepared positive pole piece, negative pole piece, electrolyte and diaphragm into the CR2032 button cell in a glove box filled with argon.

Example 2

The difference from the embodiment 1 lies in:

the ceramic separator includes a base film 1 and ceramic coatings 2 disposed on both sides of the base film 1. As shown in fig. 2 and 4, the ceramic coating layers 2 are disposed on both sides of the base film 1, wherein fig. 2 shows the filling effect of the inorganic filler, the long nanowire material and the short nanowire material, and the inorganic filler, the long nanowire material and the short nanowire material are reasonably matched and filled to form the inorganic coating layer, so that the inorganic coating layer has good mechanical strength, high temperature resistance and liquid absorption rate.

The rest is the same as embodiment 1, and the description is omitted here.

Example 3

The difference from the embodiment 1 is that:

the ceramic separator includes a base film 1 and a ceramic coating layer 2 disposed on one side of the base film 1. As shown in fig. 5, one side of the base film 1 is provided with a ceramic coating layer 2, so that the entire separator has good mechanical strength, high temperature resistance, and liquid absorption rate.

The rest is the same as embodiment 1, and the description is omitted here.

Example 4

The difference from the embodiment 1 is that:

the ceramic separator includes a base film 1, a ceramic coating layer 2 disposed on one side of the base film 1, and a polymer coating layer 3 disposed on one side of the base film 1 remote from the ceramic coating layer 2. As shown in fig. 6, a ceramic coating 2 is disposed on one side of a base film 1, a polymer coating 3 is disposed on the other side of the base film 1, and the ceramic coating 2 and the polymer coating 3 are used in combination, so that the whole diaphragm has good mechanical strength, high temperature resistance and liquid absorption rate.

The rest is the same as embodiment 1, and the description is omitted here.

Example 5

The difference from the embodiment 1 is that: a method for preparing a ceramic diaphragm, which comprises the following steps,

the weight part ratio of the inorganic filler to the nanowire material is 30: 50.

the rest is the same as embodiment 1, and the description is omitted here.

Example 6

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler to the nanowire material is 70: 50.

the rest is the same as embodiment 1, and the description is omitted here.

Example 7

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler to the nanowire material is 50: 20.

the rest is the same as embodiment 1, and the description is omitted here.

Example 8

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler to the nanowire material is 50: 30.

the rest is the same as embodiment 1, and the description is omitted here.

Example 9

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler to the nanowire material is 50: 80.

the rest is the same as embodiment 1, and the description is omitted here.

Example 10

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler, the first dispersing agent, the first thickening agent, the first wetting agent and the first binder is 30:0.5:0.5: 0.5: 0.1.

the rest is the same as embodiment 1, and the description is omitted here.

Example 11

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler, the first dispersing agent, the first thickening agent, the first wetting agent and the first binder is 30:0.5:0.5: 0.5: 0.5.

the rest is the same as embodiment 1, and the description is omitted here.

Example 12

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler, the first dispersing agent, the first thickening agent, the first wetting agent and the first binder is 30:0.5:0.5: 0.5: 6.

the rest is the same as embodiment 1, and the description is omitted here.

Example 13

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler, the first dispersing agent, the first thickening agent, the first wetting agent and the first binder is 30:1: 2: 1: 6.

the rest is the same as embodiment 1, and the description is omitted here.

Example 14

The difference from the embodiment 1 is that:

the weight part ratio of the inorganic filler, the first dispersing agent, the first thickening agent, the first wetting agent and the first binder is 30:1:1:1: 8.

the rest is the same as embodiment 1, and the description is omitted here.

Example 15

The difference from the embodiment 1 is that:

the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 50:1:1:1: 0.5.

The rest is the same as embodiment 1, and the description is omitted here.

Example 16

The difference from the embodiment 1 is that:

the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 40:1:1:1: 0.5.

The rest is the same as embodiment 1, and the description is omitted here.

Example 17

The difference from the embodiment 1 is that:

the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 30:1:1:1: 5.

The rest is the same as embodiment 1, and the description is omitted here.

Example 18

The difference from the embodiment 1 is that:

the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 30:8:8:8: 0.5.

The rest is the same as embodiment 1, and the description is omitted here.

Example 19

The difference from the embodiment 1 is that:

the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 30:5:5:5: 0.5.

The rest is the same as embodiment 1, and the description is omitted here.

Example 20

The difference from the embodiment 1 is that:

the weight part ratio of the polymer main material, the second dispersing agent, the second thickening agent, the second binder and the second wetting agent is 30:2:2:2: 0.5.

The rest is the same as embodiment 1, and the description is omitted here.

Comparative example 1

5umPE base material and conventional ceramic slurry on the market are prepared, and a diagonal roll gravure coater is used for coating 2um ceramic coating 2 on the surface of the base material to obtain the conventional ceramic membrane.

Performance testing

1. And (3) testing the nail penetration safety: the lithium ion battery is fully charged, then a high-temperature-resistant steel needle (the taper angle of a needle point is 45-60 degrees, the surface of the steel needle is smooth and clean, rust-free, oxidation layer-free and oil-free) with the diameter phi of 1mm and the diameter phi of 3mm is used respectively, the high-temperature-resistant steel needle penetrates through the lithium ion battery from the direction perpendicular to a polar plate of the lithium ion battery at the speed of (25 +/-5) mm/s, the penetrating position is close to the geometric center of the surface of the punctured polar plate, the steel needle stays in the lithium ion battery, the lithium ion battery passes a nail penetration test if the steel needle does not ignite or explode after 1h observation, and the test result is recorded in a table 1.

2. And (3) liquid absorption amount test: during testing, the diaphragm sample is cut into a certain size, the diaphragm sample is soaked in the electrolyte for 0.5h at normal temperature, the weight difference of the diaphragm sample per unit area before and after soaking is the liquid absorption amount, and the test result is recorded in table 1.

3. And (3) testing the safety of the hot box: charging the lithium ion battery to 4.3V at a constant current of 1C at 25 ℃, then charging to a current of less than 0.05C at a constant voltage of 4.3V, and stopping charging; the lithium ion battery is placed in a hot box, the temperature is increased from 25 ℃ to 150 ℃ at the temperature increase rate of 5 ℃/min, the temperature is kept unchanged after the temperature reaches 150 ℃, then timing is started until the surface of the lithium ion battery starts to smoke, and the test result is recorded in table 1.

4. And (3) testing tensile strength: the diaphragm is placed on a cutting machine and cut into strip-shaped test sample strips with the width of 15mm, the diaphragm sample is marked at the position of a 10cm distance between the test sample strips, the diaphragm sample is fixed on a universal testing machine, the measurement is started, in the process that the diaphragm is pulled to be broken, the stress-strain curve is recorded, the tensile strength value of the diaphragm sample is obtained, and the test result is recorded in a table 1.

TABLE 1

As can be seen from table 1, the ceramic separator of the present invention has good mechanical strength, high temperature resistance, good liquid absorption rate for electrolyte, and a small thickness. The invention uses the matching use of the inorganic coating and the organic coating, so that the prepared ceramic diaphragm not only has the basic function of the ceramic diaphragm, but also has better high-temperature thermal shrinkage performance, puncture resistance and mechanical strength, and particularly solves the problem that the thermal shrinkage of the 1 mu m coating is larger at 150 ℃, and the thermal shrinkage of the 1 mu m coating is less than 5 percent at 150 ℃ for 0.5 h. From a comparison of examples 1 to 4, it can be seen that the ceramic coatings according to the inventionThe layer 2 can improve the mechanical strength of the diaphragm, such as puncture strength, cell bending strength and tensile strength, and simultaneously improve the wettability of the diaphragm, such as liquid absorption rate, liquid retention rate and ionic conductivity, and the polymer coating 3 can improve the bonding strength of the diaphragm. From the comparison of examples 5 to 9, it can be seen that the respective performances are better when the weight part ratio of the inorganic filler to the nanowire material is set to 50:50, and from the comparison of examples 10 to 14, when the weight part ratio of the inorganic filler, the first dispersant, the first thickener, the first wetting agent and the first binder is set to 50: 0.5: 0.2: 4: when 0.2, the prepared diaphragm has better performances; from comparison of examples 15-20, it can be seen that when the weight part ratio of the polymer main material, the second dispersant, the second thickener, the second binder and the second wetting agent is 30:0.5:0.5:1:0.5, the prepared separator has better performances. As can be seen from the results of the wettability tests in fig. 9 and 10, in the testing method, a 1ml syringe is used for taking 1ml of electrolyte, and the wettability of the diaphragm to the electrolyte is compared by observing the diffusion area of 1 drop of electrolyte in 1min in the diaphragm with the same area, where the wettability area of the diaphragm to the electrolyte in this embodiment 1 is approximately equal to the circular area with the radius of 2, that is, 12.56cm²And the wetting performance of the diaphragm of the comparative example 1 on the electrolyte is more than 1cm²Less than the area of a circle with a radius of 2, the wettability is poor.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.